Quantitative generation of singlet (1Δg) oxygen from acidified aqueous peroxynitrite produced by the reaction of nitric oxide and superoxide anion

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Abstract
Simple acidification of aqueous alkaline peroxynitrite quantitatively generates singlet (1Δg) molecular oxygen, detected and quantitated spectroscopically (1270 nm). This observation provides a chemical basis for physiological cytotoxicity of ONOO− generated in the diffusion ‐ controlled reaction of cellular NO• and O . The experiments consist of (i) chemical generation of ONOO− from NO• gas and KO2 powder in alkaline aqueous solution; (ii) absorption spectral identification of ONOO− in the near‐UV with maximum at 302 nm; (iii) spectroscopic identification of 1O2 by its emission band at 1200–1340 nm with maximum at 1275 nm; and (iv) quantitation of 1O2 generated in ONOO−/H+ reaction by comparison of the chemiluminescence intensity at 1270 nm with that from H2O2/OCl− reaction that generates 1O2 with unit efficiency at alkaline pH. 1O2 was generated with unit efficiency with respect to ONOO− concentration by the ONOO−/H+ reaction.